Sarcopenia is the age-related decline in skeletal muscle mass concomitant with decreased strength and/or function. All hospitalization, sarcopenia malignancies, conditions related to reduced muscle activity predispose to sarcopenia (e.g., sedentary lifestyle, immobilization, prolonged bed rest). Certain diseases can also promote the development of through chronic inflammation and metabolic derangements, such as endocrine disorders, chronic inflammatory diseases, and advanced organ failure (heart, lung, liver, kidney or brain). Sarcopenia has been linked to falls, physical frailty and disability. A valid measure of physical function, such as the PROMIS physical function item bank, can help evaluate whether new therapies for sarcopenia can produce an overall benefit to the patient. Our primary aims for the current proposal are to respond to the FDA request to our approved COA Letter of Intent (DDT #085), to (1) develop an appropriate context of use and (2) develop a fit-for-purpose measure of physical function for patients with sarcopenia. In November, 2015, our team of researchers at Northwestern University received a request from the Division of Endocrine/Metabolism at the US Food and Drug Administration (FDA). Highlighting an unmet need for well-defined and reliable outcome assessment of physical function in sarcopenia, the FDA asked us to submit the PROMIS measure of Physical Function as a clinical outcome assessment (COA) under their Drug Development Tools (DDT) qualification program. Based on feedback we received form the FDA on our initial Letter of Intent, our work on this initiative will begin by identifying one or more specific contexts of use (COUs) in which the assessment of physical function serves as the primary metric for labeling claims related to sarcopenia. Insights from our expert consultants will greatly influence these decisions. We will also solicit patient and other expert feedback to develop a targeted PROMIS Short Form of Physical Function for use in patients with sarcopenia. This work will put us closer to developing a qualification plan for submission to the FDA that will detail the development of the Physical Function item bank and present relevant PROMIS Physical Function data to support the validity of the bank (or short forms derived from the bank) for patient reported clinical trial outcomes. At the end of the year of funding, we anticipate having a targeted PROMIS Physical Function short form that can be further tested and used within clinical trials to benefit patients with sarcopenia.